We propose to continue the investigation of the factors involved in the relation of protein-protein interactions to enzymatic activity. Two purified enzyme systems will be used: phosphofructokinase and glutamate dehydrogenase. Techniques to be used include stopped flow light scattering and activity measurements. The effect of small molecule ligands on the rates and extents of association-dissociation reactions will be measured. Data will be analyzed with computer programs previously developed in this laboratory.